docstr: Runs the secant method for interval [z_low, z_high] for n_secant_steps 
docstr_tok: ["Runs","the","secant","method","for","interval","[","z_low",",","z_high","]","for","n_secant_steps"]
code: def secant(
      self,
      sdf_low,
      sdf_high,
      z_low,
      z_high,
      cam_loc,
      ray_directions,
      sdf,
  ):
      """Runs the secant method for interval [z_low, z_high] for n_secant_steps"""
  
      z_pred = (
          -sdf_low * (z_high - z_low) / (sdf_high - sdf_low) + z_low
      )
      for i in range(self.n_secant_steps):
          p_mid = cam_loc + z_pred.unsqueeze(-1) * ray_directions
          sdf_mid = sdf(p_mid)
          ind_low = sdf_mid > 0
          if ind_low.sum() > 0:
              z_low[ind_low] = z_pred[ind_low]
              sdf_low[ind_low] = sdf_mid[ind_low]
          ind_high = sdf_mid < 0
          if ind_high.sum() > 0:
              z_high[ind_high] = z_pred[ind_high]
              sdf_high[ind_high] = sdf_mid[ind_high]
  
          z_pred = (
              -sdf_low * (z_high - z_low) / (sdf_high - sdf_low) + z_low
          )
  
      return z_pred
  
file_path: insightface/reconstruction/PBIDR/code/model/ray_tracing.py
imports: import torch
  import torch.nn
  from utils import rend_util
label_desc: Use image node_id 5 for calling the RayTracing obj's underlying member method code with example usage: obj.secant(sdf_low, sdf_high, z_low, z_high, cam_loc, ray_directions, sdf) and returns: z_pred